The United States has long been the world’s drug cop, but now that it has abandoned the beat by allowing nine states to legalize weed, international laws preventing countries from setting their own policies on marijuana are basically unenforceable. Canada’s move could make that situation permanent.

"I think it’s a real shock to the international treaties and agreements that have held countries back from going against the hysteria that has come out of the US," said Kassandra Frederique, New York State director for the Drug Policy Alliance.

“It sends a big message,” agreed Sanho Tree, director of the Drug Policy Project at the Institute for Policy Studies, a Washington think tank, noting that Canada was among America’s most important trading partners, and happens to share a massive border.

Even the staunch legalization opponents at Smart Approaches to Marijuana admitted in a powerpoint presentation that “legalization is now a reality and it’s gaining support every year.”

“To put it very simply, Canada legalizing marijuana is huge,” added Tom Angell, editor in chief of Marijuana Moment, one of the leading online sources for marijuana news and a longtime legalization activist. “While it’s the second country to do it, it’s the first major global economic player to do so.”

While Canada’s move marks the crossing of the Rubicon, it may never have happened if the United States hadn't first gotten out of the way. America has long been both the main cheerleader for and the chief enforcer of international prohibition. During the Cold War, drug enforcement took on an outsized power because it was one of the few issues on which the United States, Russia and China could agree and collaborate.

But since 2012, when Colorado and Washington voted to become the first states to legalize recreational use and the Obama administration chose to let those states proceed, the US has been mostly silent, with one notable exception. In 2014, William Brownfield, assistant secretary of state for international narcotics and law enforcement affairs, told reporters covering the UN that the world must “tolerate different national drug policies” and “accept the fact that some countries will have very strict drug approaches," while others “will legalize entire categories of drugs."

He called for “flexible” interpretation of the Single Convention on Narcotic Drugs of 1961 and its later updates—even though neither the US nor the International Narcotics Control Board, which is part of the UN’s drug policy apparatus, had previously interpreted these laws as allowing anything close to legalization of any currently illegal substance.

Indeed, the US has long used both hard and soft power to attempt to deter even the most minor drug policy reforms. Between 1986 and 2002, America had a much-hated “certification” policy for countries seen as major sources of drugs, mainly consisting of those in Latin America. Under this process, these nations were rated by American politicians annually for their level of compliance with Uncle Sam’s drug enforcement priorities. Countries that were de-certified could lose access to almost all American aid they received—and could even be barred from getting international loans.

Not surprisingly, this one-sided policy was resented—and for a long time, it allowed the US to pretty much prevent even the smallest attempts to liberalize drug policy from taking hold.

In 2001, for example, when a Jamaican government panel recommended decriminalization of possession of marijuana within its own borders—not legalization of sales, just eliminating arrests for personal possession—the US embassy told media it was opposed to the policy and overtly threatened that if it went forward, the country might be decertified. Despite some of its people observing a religion in which marijuana is a sacrament, the government backed off. And in 2006, Mexican President Vicente Fox refused to sign a bill decriminalizing drug possession that he himself had promoted after the United States publicly pressured him not to do it.

The US has even tried to stop other countries, including European powers, from using and promoting proven policy measures now known as "harm reduction," like needle exchanges to prevent HIV. According to Tree, at the annual meeting of the UN’s Commission on Narcotic Drugs (CND), "There was a charade for years in which the US fought against using the term 'harm reduction' and went after other countries for doing so."

In fact, when Canada sought to open North America’s first safe-injection facility in 2003, a US consulate representative told the founders of the program that America forbade it, according to Travis Lupick’s important new history, Fighting For Space. Canada went forward anyway. That may have been an encouraging precedent for Canada’s new push toward legalization amid the abject failure of America’s century-long moral crusade.

For her part, Emily Dufton, author of Grass Roots: The Rise and Fall and Rise of Marijuana in America, was less sure than others I spoke to that Canada’s move really will serve as the final nail in prohibition’s coffin. She noted that in the 1970s, marijuana was nearly decriminalized nationally in the US before fears about rising teen use were used to create a massive backlash. Fewer mistakes are being made by legalizers now, she noted, however, adding, “I’m closer to getting more convinced.”

Canada’s legalization law leaves the details of regulating sales to its provinces, which will result in regimes that vary in their degree of strictness and commercialization. Some provinces will allow commercial sales; others will only allow government-run stores to sell cannabis; some may allow public consumption in “cannabis lounges” while others restrict it to private homes. Conveniently, this diversity will allow researchers to study which approaches work best.

Meanwhile, more than 60 percent of Americans—including a majority of Republicans, according to a Gallup poll last year—now support marijuana legalization. And even long-time opponents like New York Governor Andrew Cuomo are coming around (a senior official told the New York Times that the governor now sees legalization not as a matter of if, but how). That makes Canada’s move all the more propitious. On Wednesday, in fact, Senate Minority leader Chuck Schumer, a longtime drug warrior, introduced legislation to decriminalize marijuana on a federal level by removing it from the government’s list of controlled substances.

America has also lost more recent battles to stop progress elsewhere: Jamaica finally decriminalized in 2015, Mexico began decriminalizing in 2009 and moved to legalize growth for personal use in 2015. And several years ago, according to Tree, Germany led a rebellion that put an end to the anti-harm reduction language battles at the CND. Heroin prescribing for the treatment of addiction is now legal in Germany, Switzerland, the UK, the Netherlands and Denmark.

Although Russia has condemned Canada’s new law, there are no real enforcement mechanisms for the UN narcotics treaties—and Moscow seems unlikely to sanction or declare war on Canada by itself over weed.

That means that the world’s tenth-largest economy will have a massive new source of revenue that the US, as a whole at least, is denied. And American customs and border agents will have a major new headache until lawmakers admit pot prohibition is well and truly dead and legalize already.